Various edging devices have been used in attempts to define permanent grass boundaries in lawns. Such edging devices are intended to serve one or more of three general functions. Their primary purpose is to resist the encroachment of grass into flower beds or other areas where grass is not desired. In addition, some types of edging devices provide a solid surface, at grass level, for lawnmower wheels. This can be a significant convenience. Finally, some edging devices are considered to be ornamental, improving the appearance of a lawn and garden.
Elongated wood pieces or strips such as two-by-fours or railroad ties are often used as edging devices. In the case of two-by-fours, they are generally anchored or retained by stakes. Railroad ties are usually retained solely by their own weight. The primary advantage of wood is low cost. Depending upon the width of material used, wood edging devices also provide a surface for lawnmower wheels. However, untreated wood tends to rot and decay. Furthermore, wood edging devices tend to loosen and move. Many wood edging systems thus need replacement or re-setting after several years.
Thin strips or plates of metal or plastic are also used as lawn edging. The material of these devices tends to last longer than wood. However, such devices generally provide no support for lawnmower wheels. In fact, after repeated mowings the weight and movement of a lawnmower over such metal or plastic strips can tend to move or dislodge them from their desired location. Furthermore, thin strips are simply not substantial enough separate materials from each other. For instance, grass often grows right over the top of thin strips, sometimes dislodging or loosening them in the process. Bark and rock are also easily thrown from one side to the other of thin strips. Another disadvantage of these edging devices is that they provide no ornamental function.
A continuously-poured curb-like concrete edge is an alternative to the above devices. It is becoming increasingly popular. A poured concrete edge tends to be more solid and permanent than the devices described above. In addition, it provides a solid edge surface for lawn mowing and is considered by many to be aesthetically pleasing. The primary disadvantage of concrete edging systems is their high cost. Another disadvantage is that ground heaving from seasonal ground freezing and thawing can result in cracking. Ground heaving can even, in some cases, dislodge or move poured concrete edges.
Discrete concrete blocks are sometimes used instead of continuously-poured concrete edges. Blocks are lower in cost and can be easily installed by a home-owner, while possessing several of the advantages of continuously-poured concrete edges. For instance, concrete blocks are aesthetically pleasing and provide a convenient surface for lawnmowers. A significant disadvantage of discrete concrete blocks, however, is their relative instability. Ground heaving and vegetation growth tend to dislodge concrete blocks from their initial aligned positions. Foot traffic and lawnmower wheels can also shift such blocks--especially in wet conditions where the underlying ground is soft.
The invention described below is an edging system which exploits the advantages of discrete concrete blocks. However, the resulting concrete block lawn edge also has the advantage of poured concrete edges. The disadvantages of more conventional concrete block edging systems are avoided by positioning and restraining the blocks in such a way as to resist their movement and migration. A concrete block lawn edge in accordance with the invention is significantly less expensive than a poured concrete lawn edge and only slightly more expensive than a lawn edge formed by a conventional installation of discrete concrete blocks.